The present invention relates to a valve such as is suitable for switching cooling fluid flows in an internal combustion engine cooling system, and more particularly relates to a valve such as is suitable for such use in a particular type of internal combustion engine cooling system which provides either combined cooling for a cylinder head and a cylinder block of the engine, or either partly or totally separated cooling for the cylinder head and the cylinder block, according to operational conditions.
The concept of the cooling system which will be later described as a particular preferred use for the valve of the present invention is more particularly described in U.S. Pat. No. 4,370,950 issued Feb. 1, 1983 made by the same applicant as the present application and assigned to the same assignee, and based upon prior Japanese patent application Ser. No. 169933/80, priority of which was claimed, which was filed on Dec. 2, 1980, i.e. previous to the filing on Feb. 16, 1981 of the earliest of the parent Japanese patent applications of the present application of which priority is being claimed in the present application. In fact, this previous prior art invented by the same inventor as the present invention was in its turn based upon a prior art engine cooling system and method developed by a colleague of the present inventor, for which previous concept Japanese Patent Application No. 68036/80 was filed, and for which prior art concept also it is known to the present inventor that the application for U.S. Pat. No. 4,369,738 was filed Nov. 28, 1981 previous to the filing of the above identified previous U.S. application and of the present application, claiming the priority of said previous Japanese application No. 68036/80. All said previously applied Japanese and U.S. patents and applications relating to said prior art concepts have been assigned to the same assignee as is the present application; and the present inventor hereby desires to acknowledge his debt to this previous proposal by said colleague, and to incorporate the subject matter of U.S. Pat. No. 4,369,738 as well as the subject matter of his own above identified previous U.S. Pat. No. 4,370,950 by reference into the present application, by way of background prior art.
There are various considerations which arise with regard to the cooling of internal combustion engines which are cooled by the circulation of liquid cooling fluid in passages or cooling jackets formed in the cylinder head and in the cylinder block thereof. Some of these considerations relate to the cooling of the cylinder head, and others to the cooling of the cylinder block. Nowadays the prior art type old or conventional ways of cooling an internal combustion engine, in which the cooling fluid for the cylinder head was always completely mixed with that for the cylinder block, thus ensuring that the cylinder head and the cylinder block were always kept at substantially the same temperature, have become inadequate.
One of these considerations is that it is important to maximize the thermal efficiency of an internal combustion engine, and in order to do this it is effective to increase the compression ratio of the engine. However, increase of the compression ratio of the engine is limited by the occurrence of so called knocking or pinging, i.e. of detonation caused by compression ignition, not caused by any spark from a spark plug, of the air-fuel mixture within the combustion chambers of the engine. The occurrence of knocking is generally reduced by keeping the cylinder head as cool as possible, and accordingly when an internal combustion engine is being operated, especially in operational conditions in which the occurrence of knocking is a high possibility such as high rotational speed high engine load operational conditions, it is very important to cool the cylinder head down to as low a temperature as possible, consistent with other operational considerations.
On the other hand, it is not very advantageous to cool down the cylinder block of the engine to a very low temperature, because in that case the temperature of the lubricating oil contained within the cylinder block, which is of course strongly influenced by the temperature of the cylinder block, becomes rather low, thus increasing the viscosity of this lubricating oil and causing unacceptably high mechanical energy losses in the engine. Further, because the viscosity of the lubricating oil within the cylinder block when this oil is cold, i.e. when it is not at proper operating temperature, is higher than when said lubricating oil is at operating temperature, therefore of course while this lubricating oil is cold this causes substantially increased use of fuel by the internal combustion engine, which is very wasteful. Further, if the temperature of the walls of the cylinders of the engine, i.e. the temperature of the bores thereof, becomes low, then the amount of noxious components in the exhaust gases emitted by the engine rises, which can cause a serious problem in view of the standards for control of pollution by automobiles, which are becoming more and more severe nowadays.
Another problem that occurs if the temperature of the cylinder block gets low is that wear on the various moving parts of the internal combustion engine, especially bore wear, rises dramatically. In fact, a large proportion of the wear on the bores of an internal combustion engine occurs when the engine is in the non fully warmed up condition, both because the lubricating qualities of the lubricating oil in the engine are not good at low temperatures, and also because the state of mechanical fit to which the parts of the engine are "worn in" or "run in" is appropriate to their physical dimensions when at proper engine operating temperature, and accordingly in the cold or the semi cold condition these parts do not mate together very well.
These problems that arise when the cylinder block of an internal combustion engine becomes too cold during actual running operation of the engine of course also apply with equal force during the warming up process of the internal combustion engine, after it has been started up from the cold condition and before it has attained normal operating temperature. Especially, the problem of excessive wear on the moving parts of the internal combustion engine, and the problem of excessive emission of noxious components in the exhaust gases of the internal combustion engine, are particularly serious during warming up operation. In fact, in view of this matter, it has in the past been an important design goal in the designing of internal combustion engines for the moving parts thereof to be warmed up as soon as practicable, or at any rate for these moving parts to be brought to an intermediate temperature higher than a very cold non operating temperature as soon as practicable.
According to these considerations, it is important to warm up the cylinder block of an internal combustion engine as quickly as possible, when the engine is started from the cold condition, and to keep the cylinder block at quite a high operating temperature thereafter. A difficulty arises in this regard, because during the operation of an internal combustion engine most of the heat which is being generated in the combustion chambers thereof by combustion of air-fuel mixture therein is in fact communicated not to the cylinder block of the engine, but to the cylinder head thereof. Therefore transfer of heat from the cylinder head wherein said heat is mostly generated to the cylinder block is very important, especially during the warming up process of the engine. Of course, such heat transfer can take place by the usual process of heat conduction, since the cylinder head is clamped to the cylinder block, typically however with the interposition between of a head gasket which may have a rather low heat conductivity. However, it is desirable to convey heat from the cylinder head to the cylinder block during engine warmup more quickly than can be accomplished by this conduction process, and the conventional above described mixing of the cooling fluid circulating within the cylinder head with the cooling fluid circulating within the cylinder block during engine warmup is effective for achieving this.
In the prior art previous to the above particularly identified commonly assigned proposals, it has been proposed to provide completely independent systems for cooling the cylinder head and for cooling the cylinder block, in order to fulfill the first above described objective of cooling the cylinder head to a low temperature in order to avoid knocking, while keeping the cylinder block warmer, and each of these systems has been equipped with its own cooling fluid pump, conduits, radiator etc. However, such a system does not provide for the above described transfer of heat during the engine warming up process from the cylinder head to the cylinder block via the cooling fluid, and since the cylinder block has a considerably large heat capacity this means that the cylinder block does not warm up quickly from the cold condition, with the ill effects detailed above. Also, the provision of two independent cooling systems increases weight to an unacceptably high extent, and increases manufacturing cost. Further, since in the above described system two independent radiators are used, and the flow amount through each of them is individually regulated, it is very difficult to use total radiator cooling capacity fully, because although in some particular set of operational conditions the full cooling capacity of one radiator of one cooling system may not be completely required, it is not practicable to utilize this spare cooling capacity in order to provide additional cooling in the other cooling system, and accordingly one cooling system may become overloaded, while the other is not fully loaded. This operational inflexibility is very troublesome.
Therefore, in the previous proposal by the same inventor as the present application, i.e. the proposal of U.S. patent application Ser. No. 264,866, there was proposed, for an internal combustion engine comprising: (a) a cylinder head formed with a head cooling jacket for cooling said cylinder head, said head cooling jacket being formed with a cylinder head inlet and a cylinder head outlet; (b) a cylinder block formed with a block cooling jacket for cooling said cylinder block, said block cooling jacket being formed with a cylinder block inlet and a cylinder block outlet; and (c) a radiator formed with an inlet and an outlet; a cooling system, comprising: (d) a first pump for impelling cooling fluid through said head cooling jacket from said cylinder head inlet towards said cylinder head outlet; (e) a second pump for impelling cooling fluid through said block cooling jacket from said cylinder block inlet towards said cylinder block outlet; (f) a block recirculation conduit system leading from said cylinder block outlet of said block cooling jacket so as to supply flow of cooling fluid, from a downstream part of said block recirculation conduit system, to said cylinder block inlet of said block cooling jacket; (g) a main recirculation conduit system, an upstream part of which is communicated to said cylinder head outlet of said head cooling jacket, and a downstream part of which is communicated to said inlet of said radiator; (h) a radiator output conduit system, leading from said outlet of said radiator to said cylinder head inlet of said head cooling jacket; (i) a first junction assembly between said block recirculation conduit system and said main recirculation conduit system at upstream parts thereof, which at least sometimes allows flow between said part of said block recirculation conduit system and said part of said main recirculation conduit system; (j) a second junction assembly between a downstream part of said block recirculation conduit system and a part of said radiator output conduit system, which at least sometimes allows flow between said part of said block recirculation conduit system and said part of said radiator output conduit system; (k) and a mechanical non-electrical control valve assembly which is incorporated in said first junction assembly and said second junction assembly and which controls the allocation of flow through said head cooling jacket and flow through said block cooling jacket between said block recirculation conduit system and said main recirculation conduit system, according to a set of parameters which include the temperature of the cooling fluid passing out of said block cooling jacket; (l) wherein said control valve assembly: when it detects a temperature of the cooling fluid flow passing out of said block cooling jacket of less than a first predetermined temperature, is so switched that it directs substantially all the cooling fluid flow through said head cooling jacket which is passing out through said cylinder head outlet and also substantially all the cooling fluid flow through said block cooling jacket which is passing out through said cylinder block outlet to flow into said upstream part of said block recirculation conduit system, not directing any substantial cooling fluid flow into said upstream part of said main recirculation conduit system; when it detects a temperature of the cooling fluid passing out of said block cooling jacket of greater than said first predetermined temperature but less than a second predetermined temperature greater than said first predetermined temperature, is switched so that it directs substantially all the cooling fluid flow through said head cooling jacket which is passing out through said cylinder head outlet to flow into said upstream part of said main recirculation conduit system and through said radiator, and so that it directs substantially all the cooling fluid flow through said block cooling jacket which is passing out through said cylinder block outlet to flow into said upstream part of said block recirculation conduit system; and, when it detects a temperature of the cooling fluid passing out of said block cooling jacket of greater than said second predetermined temperature, is so switched that it directs substantially all the cooling fluid flow through said head cooling jacket which is passing out through said cylinder head outlet and also substantially all the cooling fluid flow through said block cooling jacket which is passing out through said cylinder block outlet to flow into said upstream part of said main recirculation conduit system and through said radiator, said two cooling fluid flows being mixed within said main recirculation conduit system and within said radiator, not directing any substantial cooling fluid flow into said upstream part of said block recirculation conduit system.
By such a construction, before said internal combustion engine has warmed up to said first predetermined temperature: all of said cooling fluid flowing through said head cooling jacket and also all of said cooling fluid flowing through said block cooling jacket pass out of said cylinder head outlet and said cylinder block outlet respectively, then meet in said first junction assembly and both enter into said block recirculation conduit system, then flow down said block recirculation conduit system and diverge in said second junction assembly, said head jacket cooling fluid flow then entering into said radiator output conduit system and passing to said cylinder head inlet, while said block jacket cooling fluid flow passes down said block recirculation conduit system to said cylinder block inlet, neither of said cooling fluid flows therefore passing through said radiator so that neither of them is substantially cooled; when said internal combustion engine has been warmed up to a temperature above said first predetermined temperature but below said second predetermined temperature: said cooling fluid flowing through said head cooling jacket passes out of said cylinder head outlet and past said first junction assembly to flow down said main recirculation conduit system, through said radiator wherein it is cooled, down said radiator output conduit system, past said second junction assembly, and down said radiator output conduit system to said cylinder block inlet, while said cooling fluid flowing through said block cooling jacket passes out of said cylinder block outlet and past said first junction assembly to flow down said block recirculation conduit system, past said second junction assembly, and down said block recirculation conduit system to said cylinder block inlet, not being substantially cooled; and, after said internal combustion engine has been warmed up to a temperature above said second predetermined temperature, all of said cooling fluid flowing through said head cooling jacket and also all of said cooling fluid flowing through said block cooling jacket pass out of said cylinder head outlet and said cylinder block outlet respectively, then meet in said first junction assembly and both enter into said main recirculation conduit system, pass while mixing through said radiator wherein they are cooled, and then pass down said radiator output conduit system and diverge in said second junction assembly, said head jacket cooling fluid flow then continuing down said radiator output conduit system and passing to said cylinder head inlet, while said block jacket cooling fluid flow passes down said block recirculation conduit system to said cylinder block inlet, both of said cooling fluid flows therefore passing through said radiator so that both of them are substantially cooled.
Further, according to that previous proposal, there was also proposed a structure for said control valve, comprising: a valve casing formed with a first port, a second port, a third port, and a fourth port; a first valve element and a first valve seat cooperating with said first valve element so as to open and close a first controlled aperture through said first valve seat, said first controlled aperture being on a first fluid flow path between said first port and said third port and being the only controlled aperture thereon, and also being on a third fluid flow path between said second port and said third port; a second valve element and a second valve seat cooperating with said second valve element so as to open and close a second controlled aperture through said second valve seat, said second controlled aperture being on a second fluid flow path between said first port and said fourth port; a third valve element and a third valve seat cooperating with said third valve element so as to open and close a third controlled aperture through said third valve seat, said third controlled aperture being on said third fluid flow path between said second port and said third port, said first and third controlled apertures being the only controlled apertures on said third fluid flow path between said second port and said third port; a fourth valve element and a fourth valve seat cooperating with said fourth valve element so as to open and close a fourth controlled aperture through said fourth valve seat, said fourth controlled aperture being on a fourth fluid flow path between said second port and said fourth port and being the only controlled aperture thereon, and said fourth controlled aperture also being on said second fluid flow path between said first port and said fourth port, said second and fourth controlled apertures being the only controlled apertures on said second fluid flow path between said first port and said fourth port; a first temperature sensitive actuator exposed to sense the temperature near said second port or said fourth port, which, when it senses a temperature less than said first predetermined temperature, moves said first valve element so as to press said first valve element against said first valve seat and so as to close said first controlled aperture through said first valve seat, interrupting communication between said first port and said third port via said first fluid flow path and between said second port and said third port via said third fluid flow path, and moves said second valve element so as to bring said second valve element away from said second valve seat and so as to open said second controlled aperture through said second valve seat, partially establishing communication between said first port and said fourth port via said second fluid flow path; and when it senses a temperature higher than said first predetermined temperature, moves said first valve element so as to bring said first valve element away from said first valve seat and so as to open said first controlled aperture through said first valve seat, establishing communication between said first port and said third port via said first fluid flow path and partially establishing communication between said second port and said third port via said third fluid flow path, and moves said second valve element so as to press said second valve element against said second valve seat and so as to close said second controlled aperture through said second valve seat, interrupting communication between said first port and said fourth port via said second fluid flow path; a second temperature sensitive actuator exposed to sense the temperature near said second port or said fourth port, which, when it senses a temperature less than said second predetermined temperature, moves said third valve element so as to press said third valve element against said third valve seat and so as to close said third controlled aperture through said third valve seat, interrupting communication between said second port and said third port via said third flow path, and moves said fourth valve element so as to bring said fourth valve element away from said fourth valve seat and so as to open said fourth controlled aperture through said fourth valve seat, establishing communication between said second port and said fourth port via said fourth fluid flow path and partially establishing communication between said first port and said fourth port via said second fluid flow path; and when it senses a temperature higher than said second predetermined temperature, moves said third valve element so as to bring said third valve element away from said third valve seat and so as to open said third controlled aperture through said third valve seat, partially establishing communication between said second port and said third port via said third fluid flow path, and moves said fourth valve element so as to press said fourth valve element against said fourth valve seat and so as to close said fourth controlled aperture through said fourth valve seat, interrupting communication between said second port and said fourth port via said fourth fluid flow path and interrupting communication between said first port and said fourth port via said second fluid flow path.
This previously proposed structure for the control valve assembly was fairly good, but some difficulties tended to arise in practice, as follows. Because the type of control valve assembly outlined above, during its switching over period, did not particularly prevent the first valve element being moved away from the first valve seat before the second valve element had been seated against the second valve seat, thereby there was a possibility that the first port could be at once communicated to the second port and to the third port, at least for a certain transient time during the switching over of said control valve assembly. Now, with respect to the use of such a control valve assembly in a cooling system of the sort outlined above, this meant that there was a risk that, when control valve assembly transited from its operational condition in which it detected a temperature of the cooling fluid flow passing out of said block cooling jacket of less than said first predetermined temperature, to its operational condition in which it detected a temperature of the cooling fluid flow passing out of said block cooling jacket of greater than said first predetermined temperature, cold cooling fluid which had been in the upstream part of the main recirculation conduit system, or which had passed through the radiator and been cooled and had then passed through the cylinder head cooling jacket but still was rather cool, should be sucked into the upstream end of the block recirculation conduit system via the fourth port, before it was desirable to feed cooled cooling fluid into said block recirculation conduit system to cool the cylinder block. This rush of cold cooling fluid could in an extreme case cause a dangerous thermal shock to the cylinder block, thus damaging or destroying it; and in any case could severely adversely affect the operation of a heater which was being operated by using cooling fluid taken from the cylinder block cooling jacket or from the block recirculation conduit system for passing through it.